The more sounds you train for (each trained separately until the behavior is complete) the faster your dog will generalize the behavior to that sound. For example, when I started training Jessie for a door knock after learning the wake alarm, the first behavior she offered was a nose nudge.
In this situation, Jessie was also offering the nose nudge as a default behavior in a situation where she didn't know what I wanted. She was smart enough to try to offer the sound alert behavior in response to a new sound. THIS is what generalizing is.
If those first few sound alerts of the new sounds are immediately reinforced, you’ll get the alerting behavior for the new sound more quickly. If you ignore them or don’t reinforce them, your dog will be confused and not be confident in what you are asking her to do and may offer other behaviors.
If you do not use some specific sounds on a regular basis, you will need to review training on a monthly basis to keep the behavior current.
What other ways can a one and two way alert be used by Assistance Dogs?